The present invention relates to reproducing transducers having tracking control functions in apparatus for reproducing recorded signals from rotary recording mediums. More particularly, the invention relates to a reproducing transducer capable of tracking control, in an apparatus for reproducing a video signal from a rotary disc on which the video signal has been recorded on a spiral track or concentric circular tracks, in a manner such that a reproducing tracing element for reproducing the video signal accurately traces on the track.
Heretofore, there have been apparatuses of the type wherein, for example, a rotary disc on which a video signal has been recorded on a spiral track as variations in the geometrical shapes corresponding to an information content is rotated, and a reproducing transducer is caused to trace the spiral track thereby to reproduce the recorded video signal. In a reproducing apparatus of this character, it is necessary that the reproducing transducer trace the track accurately. For this reason, it is necessary to provide means for detecting any tracking deviation of the reproducing transducer relative to the above mentioned track on the rotary disc and controlling, in response to this error, the position of the reproducing transducer so that it will trace accurately over the track thereby to accomplish tracking control.
In U.S. patent application Ser. No. 785,095, entitled "Information signal recording and reproducing system", assigned to the same assignee as the present application a novel system is disclosed wherein pilot signals are previously recorded on the track of the rotary disc or in the vicinity thereof. Then, at the time of reproduction, the pilot signals are reproduced together with the video signal, and tracking of the reproducing transducer is carried out in response to the reproduced pilot signals. In this proposed system, the system for recording and reproducing the pilot signals is novel.
However, as can be observed also in this proposed system, the tracking control device comprises, as one example, a coil supplied with an error signal obtained on the basis of the above mentioned reproduced pilot signals, a support member on which is mounted a cantilever over a damping member interposed therebetween, the cantilever being provided at its outer end with a reproducing tracing element, and a movable shaft coupled to the support member and undergoing displacement in response to a current flowing through the above mentioned coil has heretofore been employed. In this device, the movable shaft undergoes displacement unitarily with the support member in response to the error signal flowing through the coil, and, as a consequence, the reproducing tracing element is displaced in the direction transverse to the longitudinal direction and is tracking controlled so as to trace accurately over the track.
This tracking control device, however, has been accompanied by the following difficulties. Since the damper member, the cantilever, and the like which are easily deformed are interposed between the movable shaft driven directly by the above mentioned coil and the reproducing tracing element for tracing the track, the reproducing tracing element cannot always undergo displacement unitarily relative to the displacement of the movable shaft, and accurate tracking control cannot be carried out. Furthermore, since the support member is adapted to be displaced in the direction transverse to the longitudinal direction of the track, it is difficult to adapt the support member to be capable of being displaced also in the longitudinal direction of the track. For this reason, it has heretofore been difficult to use a jitter compensation device for causing the reproducing tracing element to undergo displacement in the longitudinal direction of the track in combination with the above described tracking control device.